Franking machine

ABSTRACT

The invention relates to a franking machine, comprising at least one print head of an ink-jet printing mechanism for printing flat postal items such as letters or postcards, which can be introduced into said mechanism or which pass through the same. Said franking machine consists of a guiding part ( 39 ) which is located around the print head and projects in relation to the nozzle opening plane of said print head and with which a conveying device is associated, said conveying device transporting the postal items between itself and conveying rollers lying opposite and rotating about axes that are located crosswise to the conveying direction. Said conveying device has two drive-connected driving rollers ( 32, 33 ) which together with the guiding part ( 39 ), form a path of travel. The driving rollers are located in front of and behind the print head in relation to the conveying direction. A reversibly liftable counter-pressure roller ( 13, 15 ) located opposite exerts a pressure on each driving roller ( 32, 33 ), respectively, or on a postal item being transported in-between.

[0001] The invention relates to a franking machine with at least oneprint head of an inkjet printing mechanism for printing flat postalobjects, such as letters or postcards, inserted into or passing throughthe machine, comprised of a guide part arranged so as to project fromthe print head and relative to its jet opening plane and havingcorrelated therewith a transport device for transporting the postalobjects between it and oppositely positioned conveying rollers rotatingabout axes oriented transverse to the conveying direction. The frankingmachines employ today in addition to the classical rotary printingtechnology increasingly new stamp application methods, inter alia, basedon thermal or inkjet basis.

[0002] It has been shown in practice that not only the print head mustbe replaced, but depending on the printing technology the entirefranking machine configuration is subject to greater and very complex,i.e., also correspondingly expensive, changes and modifications.

[0003] Inkjet print heads have been known for quite some time and areused, in particular, in PC printers. The knowledge that has been gainedfor use of such print heads in this field cannot be transferred onto thepresent field of use in franking machines. The reasons, inter alia, liein the high speed of the letters undergoing franking as well as theirdifferent formats and thicknesses as well as the considerably rougherconditions of the surroundings, caused partially by soiled surfaces ofthe postal objects. Moreover, these franking prints must fulfill strictquality requirements of the postal offices, which make necessary highconstruction expenditure and reliability.

[0004] The object of the present invention resides in that the frankingmachine is to be configured such that it enables, provided with aninkjet print head, as much as possible a disruption-free printing forthe franking of postal objects, such as letters, cards or the like ofdifferent thickness, different formats and materials, and produces anunequivocally identifiable print image. Since presently such machinesmust enable high throughput, a fully automated operation is alsorequired.

[0005] Special importance therefore resides in the guiding of the postalobjects in the area of the print head. Since from the thinnest A objects(essentially a single sheets) to a thick letter, a wide range of postalobjects with most different mechanical properties—for example, bendingbehavior—as well as most different formats are to be printed or providedwith franking, during the entire printing phase the spacing of the jetopening plane of the inkjet print head relative to the object surface tobe printed must be constant. Moreover, conditions are to be providedwhich ensure a robust configuration, reliability, and low-maintenanceconfiguration.

[0006] In addition to these requirements a robust embodiment,reliability, low-maintenance configuration, and high-quality of theprint image are to be fulfilled.

[0007] According to the invention this object is solved in that thetransport device comprises two drive rollers connected in drivingconnection with one another and forming together with the guide part aconveying path, which drive roller, when viewed in the conveyingdirection, are arranged before and behind the print head and in that acounterpressure roller is arranged opposite thereto, respectively, whichexerts a pressure against the drive roller or the postal object to betransported therebetween and which is reversibly liftable. With thesemeasures, high precision during printing of the postal objects and ahigh-quality economical manufacture as well as a simple operation can beobtained with the franking machine according to the invention.

[0008] In the following, the functions and the configuration as well asadvantages of an embodiment of the franking machine according to theinvention with inkjet printing technology will be described. Thedescription is limited primarily in this context to the technicalfeatures for printing the postal object during the transport in thefranking machine.

[0009] For a better understanding, reference is being had to thereference numerals and Figures in which embodiments of the invention areillustrated.

[0010]1A forward control curve for right counterpressure roller

[0011]1B rear control curve for right counterpressure roller

[0012]2A forward control curve for left counterpressure roller

[0013]2B rear control curve for left counterpressure roller

[0014]3 main shaft

[0015]4 rear sidewall

[0016]5 forward sidewall

[0017]6A counterpressure lever, left, front

[0018]6B counterpressure lever, left, rear

[0019]7A control lever, left, front

[0020]7B control lever, left, rear

[0021]8A counterpressure lever, right, front

[0022]8B counterpressure lever, right, rear

[0023]9A control lever, right, front

[0024]9B control lever, right, rear

[0025]10 axle for counterpressure lever and control lever

[0026]11 stop bolt for counterpressure lever—right

[0027]12 stop bolt for counterpressure lever—left

[0028]13 counterpressure roller—right

[0029]14 support roller

[0030]15 counterpressure roller—left

[0031]16A linkage, front, for support roller

[0032]16B linkage, rear, for support roller

[0033]17 axle for linkage

[0034]18 rod for suspending spring

[0035]19 suspension location for spring

[0036]20 tension spring for control lever

[0037]21 support roller carrier with sensor member

[0038]22 cam follower

[0039]23 worm shaft

[0040]24 worm gear

[0041]25 forked light barrier

[0042]26 slotted disk

[0043]27 switching cam for initial position of main shaft

[0044]28 microswitch

[0045]29 control roller

[0046]30 tension spring for counterpressure lever

[0047]31 direct-current motor

[0048]32 drive roller, right

[0049]33 drive roller, left

[0050]34 axle for counterpressure roller, right

[0051]35 stop for cam follower

[0052]36 tension spring for cam follower

[0053]37 stop for sensor member

[0054]38 sensor wheel for incremental transponder

[0055]39 holding-down plate or guide part

[0056]40 drive motor for feed

[0057]41 gearbox for drive rollers

[0058]42 incremental transponder, encoder

[0059]43 projecting member on support roller carrier

DESCRIPTION OF THE DRAWING OF THE FOLLOWING FIGURES

[0060]FIG. 1 front view of the complete counterpressure mechanism,including drive, sensor wheel, and main shaft drive;

[0061]FIG. 2 plan view onto counterpressure mechanism according to FIG.1;

[0062]FIG. 3 front view of the complete counterpressure mechanism infranking position, counterpressure arrangement in upper position;

[0063]FIG. 4 front view of the complete counterpressure mechanism inservice position, counterpressure arrangement in lowermost position;

[0064]FIG. 5 front view, position of counterpressure lever/rollers withinserted thick short letter or letter being fed from the right byautomatic feeding into a position under the right drive roller;

[0065]FIG. 6 front view, thick letter underneath all drive rollers andthe sensor wheel;

[0066]FIG. 7 front view, thick letter has left the right roller, theright counterpressure roller automatically reaches the upper position,the central support roller remains at the initial height level. The leftcounterpressure roller has taken over the height sensing; and

[0067]FIG. 8 plan view, drive rollers with feed gear mechanism.

[0068] In the case of franking of individual letters, the letter isinserted manually into the franking machine which is in its initialposition. Phaoto cells start the franking process when the envelope iscorrectly positioned. The counterpressure rollers which are in a lowerposition upon insertion of the envelope are moved upwardly by thecontrol curves on the main shaft and press the letter object against theupper drive rollers. The letter transport or the franking process cannow be started.

[0069] The counterpressure arrangement is comprised of threecounterpressure rollers. Two rollers are positioned under the right andleft drive rollers. The third, central roller has the object to move theletter to the required height level under the print heads withoutpressing the letter against the end faces of the print heads so that theprint image remains clean without smearing. After the franking process,the counterpressure rollers move again downwardly and release the gapfor the insertion of a new envelope.

[0070] In addition to the insertion and franking position of thecounterpressure rollers, there is also a position “service”. In thisposition the counterpressure rollers are moved farther downwardly inorder to provide room for the service station. The service stationcleans and closes the print heads for longer work interruptions orduring transport of the franking machine. Moreover, it is required forfilling the print heads when changing the ink bag.

[0071] Construction and Function Descriptions of the Transport Device Onthe main shaft 3 several control curves 1A, 1B and 2A, 2B are arrangedwhich lift or lower, depending on the required position, the controllevers 7A, 7B and 9A, 9B via the control rollers 29 so as to be pivotedabout the axle 10. The initial position of the main shaft 3 is found bythe microswitch 28 switched by the control cam 27. By means of the motor31 the worm gear mechanism 23/24 is driven and the main shaft is rotatedinto the position “insertion of letter”, “franking”, or “serviceposition”. The precise position is reached by a forked light barrier 25and the slotted disc 26 seated on the motor shaft by means of electroniccontrol—as a result of the number of triggered pulses. Thecounterpressure levers to the right and left 6A, 6B and 8A, 8B arepivoted by the tension springs 30 connected to the control levers 7A, 7Band 9A, 9B in the upward direction about the axle 10 until thecounterpressure rollers 13, 15 come to rest against the upper driverollers 32, 33. The control levers 7A, 7B and 9A, 9B reach their endpositions via the control curves 1A, 1B and 2A, 2B which has the resultthat the tension springs 36 are further pretensioned by a small amount.The safe contact between the control rollers 29 and the control curves1A, 1B and 2A, 2B is achieved by the tension springs 29 connected to thespring suspension rod 18. The precise lower position of thecounterpressure levers 6A, 6B and 8A, 8B is reached at the stop bolts11, 12 on the control levers which are supported on the counterpressurelevers after a short return stroke and entrain them in the downwarddirection. The corresponding positions are illustrated in detail in theFigures.

[0072] The support roller 14 positioned at the center which moves theletter to an exact spacing relative to the inkjet print heads is seatedrotationally supported on two support roller carriers 21 which are, inturn, supported by means of two parallelogram linkages 16A, 16B. The camfollower 22 seated on the rotation axle of the support roller 14 isconnected to the axle 34 of the right counterpressure rollers 13 and isforced to move in the downward direction when lowering the rightcounterpressure lever 6A, 6B and reaches the level of the rightcounterpressure roller. The cam follower 22 is supported via the stop 35against the support roller carrier 21 rigidly in regard to rotation tothe left. With regard to rotation to the right, the cam follower 22 canrotate away from the stop 35 counter to the force of the tension spring36. This is required because of the mutual sensing between the right andthe left counterpressure roller and will be described in more detaillater on.

[0073] Description to FIGS. 1 to 8:

[0074] The counterpressure levers 6A, 6B; 8A, 8B are in the initialposition ready for insertion of an individual letter. As soon as theletter is positioned in an exact position to the rear and the rightdefined by the table stop, the franking machine is activated by means ofa reflective light barrier. First the main shaft 3 rotates aboutapproximately one-third revolution in the clockwise direction. Thecontrol levers 7, 9 are pivoted upwardly by the control rollers 29 bymeans of the control curves 1, 2. The counterpressure levers are alsomoved upwardly via the tension springs 30 until the counterpressurerollers 13, 15 rest against the drive rollers 32, 33. The control leversmove still farther until the control curve has reached its highestpoint. The possible overstroke of the control lever is compensated bythe sprung coupling of the counterpressure levers. The support roller 14has been adjusted by means of the cam follower 22 to the same level. Theletter is now clamped between the drive rollers and the counterpressurerollers. The drive motor 40 (see FIG. 8) drives via the gear mechanism41 the drive rollers 31, 33 and moves the letter from the right to theleft. The speed and position detection is realized by the incrementaltransponder 42 and the sensing wheel 38. The sensing wheel is driven byfriction by means of the moving letter envelope and detects thus theprecise speed of the letter surface. The pressing of the letter againstthe sensing wheel is realized by a separate counterpressure arrangementwhich will be described separately in the following. As a function ofthe letter position, the inkjet print heads spray corresponding linepatterns which result in the desired print image. The holding-down plateor the guide part 39 secures the letter at an exact spacing to the printhead end face in order to enable with respect to resolution a cleanprint image and, furthermore, to prevent that the printed lines smearwhen moving the envelope. After completion of the franking process thedrive motor is switched off and the main shaft returns by rotation intoits initial position; the counterpressure levers reach again theirinitial position. A new letter can be inserted. The main shaft 3 rotatesbetween the position “insertion” and “franking” only by approximatelyone-third revolution back and forth, which provides a considerable timeadvantage and moreover is gentle on the mechanism. After a furtherone-third revolution the counterpressure rollers have reached theirabsolute lowest position as is required in the service position (seeFIG. 4). Movement back into the initial position “insertion” requiresalso only one-third revolution.

[0075] In FIG. 5 the function of the cam follower 22 in connection withthe right counterpressure roller 13 is illustrated. The necessity ofthis function is described in the following. The initial position ischaracterized by a relatively thick short envelope which is insertedmanually. The franking machine triggers the franking process. Thecounterpressure levers move, as described, in the upward direction. Thethickness of the short letter limits the stroke of the rightcounterpressure roller in the upward direction. The letter is clamped bymeans of the spring force that is built up by the tension spring 19between the upper right drive roller 32 and the counterpressure roller13. This is necessary in order to ensure a slip-free drive. If thesupport roller 14 were not moved automatically by means of the camfollower 22 to the same height level, the thick envelope could not beclamped between the upper stationary holding down plate or the guidepart 39 and the support roller; this would result in transport problemsand printing quality loss. By means of the already described camfollower 22 the support roller carrier with support roller is moved tothe height level of the right counterpressure roller. The support rollercarrier moves synchronously in the form of a parallelogram with theright counterpressure roller in the downward direction and the envelopecan pass without friction through the printing station.

[0076] In FIG. 6 the illustration shows the thick letter having beenmoved also under the left drive roller. The left counterpressure leverhad to move also in the downward direction counter to the spring forceand has reached the same height level as the right counterpressure leveror the central support roller. The stop 37 of the left counterpressureroller has contacted the sensing member of the support roller carrier21.

[0077] In FIG. 7, the letter has left the right drive roller and theright counter roller moves again upwardly until the counterpressureroller contacts the upper drive roller. The stop 37 of the leftcounterpressure roller rests against the member 43 of the support rollercarrier 21 and secures it now at the original height level. The rightcam follower 22 can fold out by rotating to the left and the connectingpoint can follow the right counterpressure roller until thecounterpressure roller rests against the upper right drive roller. Theheight sensing of the support roller is realized alternatingly betweenthe right and left counterpressure roller and ensures thus over theentire letter length an optimal friction-free passage relative to theprint heads and a friction-optimized spacing relative to theholding-down plate or the guide part.

1. Franking machine with at least one print head of an inkjet printmechanism for printing flat postal objects such as letters or postcardsinsertable into or passing through the machine, comprised of a guidepart (39) arranged so as to project about the print head and furtherrelative to its jet opening plane, having correlated therewith atransport device for transporting the postal objects between it andoppositely positioned conveying rollers rotating about axes orientedtransverse to the conveying direction, characterized in that thetransport device has two drive rollers (32, 33) connected in drivingconnection with one another and forming together with the guide part(39) a conveying path, which, when viewed in the conveying direction,are arranged before and behind the print head and in that acounterpressure roller (13, 15) is arranged opposite thereto,respectively, which exerts a pressure against one drive roller (32, 33)or the postal object to be transported therebetween and which isreversibly liftable.
 2. Machine according to claim 1, characterized inthat between the counterpressure rollers (13, 15) a support roller (14)is arranged which is connected to at least one of the liftablecounterpressure rollers (13, 15) and adjustable with respect to thespacing of the guide part (39).
 3. Machine according to claim 2,characterized in that at least one of the counterpressure rollers (13,15) and the support roller (14) can be moved into an insertion position,a franking position, or a servicing position.
 4. Machine according toone of the claims 2 or 3, characterized in that the counterpressurerollers (13, 15) are supported, respectively, on controlledcounterpressure lever pairs (6A,6B; 8A,8B) which have a common pivotaxle (10).
 5. Machine according to claim 4, characterized in that thesupport roller (14) is connected by a cam follower pair (22) with atleast one of the counterpressure lever pairs (6A,6B; 8A,8B).
 6. Machineaccording to claim 4, characterized in that the counterpressure leverpairs (6A,6B; 8A,8B) are connected by a driving connection with acontrol curve pair (1A,1B; 2A,2B), respectively, arranged on amotorically driven main shaft (3) and can be moved into atransport-active position.
 7. Machine according to one of the claims 2to 6, characterized in that the counterpressure rollers (13, 15) and thesupport roller (14) can be controlled so as to be loweredsimultaneously.
 8. Machine according to one of the claims 1 to 7,characterized in that the counterpressure lever pairs (6A,6B; 8A,8B) areconnected by tension springs (36) with a counter control lever pair(7A,7B; (9A, 9B) supported on the control curve pairs (1A, 1B; 2A,2B).9. Machine according to claim 8, characterized in that the control leverpairs (7A,7B; 9A,9B) are supported on the pivot axle (10).
 10. Machineaccording to claim 9, characterized in that the control lever pairs (7A,7B; 9A,9B) are supported against spring force by means of controlrollers (29) on the control curves (1A, 1B; 2A,2B).
 11. Machineaccording to one of the claims 8 to 10, characterized in that the lowerposition of the counterpressure roller pairs (6A, 6B; 8A, 8B) is definedby a stop (11, 12) fastened on the control lever pairs (7A,7B; 9A,9B).12. Machine according to one of the claims 5 to 11, characterized inthat the support roller (14) is supported on a support roller carrierpair (21) connected to the control lever pair (7A, 7B).
 13. Machineaccording to claim 12, characterized in that the support roller carrierpair (21) is connected at the end facing away from the support roller(14) with a parallelogram linkage pair (16A, 16B) and at the supportroller end with the counterpressure roller (13) by means of the camfollower pair (22).
 14. Machine according to claim 13, characterized inthat the cam follower pair (22) is connected by tension springs with thefree end of the parallelogram linkage pair (16A, 16B).
 15. Machineaccording to claim 14, characterized in that the counterpressure leverpair (6A, 6B) is supported in the area of the counterpressure roller(15) on the parallelogram linkage pair (16A, 16B).